Before installing door and window trim first caulk around the openings to create a moisture and air proof seal.
How to install vinyl siding window trim.
Install the tops first then the sides and then the bottoms of the window surrounds.
Exterior window trim on vinyl siding if your home has vinyl siding and you d like to add vinyl window trim you will first need to remove the existing siding and j channel from around the windows.
Install the top piece of molding snapping it over the vertical side moldings.
Install door window trim.
Cut and install new j channel along the sides and top of the window.
Take the vinyl siding pieces removed earlier and cut them down to fit around the window.
Along the tops install j channel trim with horizontal siding and base trim with vertical siding.
Instruction on how to install exterior 2x4 trim around a new or old window.
Install siding at the top of a window or door in a similar fashion but this time set the siding on the window channel and use the window trim to mark the cut.